1. Field of the Invention
The present invention relates to a shift rod device for driving a transmission apparatus when a gear shift is performed by a shift pedal operation of a rider in a motorcycle.
2. Description of the Related Art
For reducing a lap time in a motorcycle being a large-sized motorcycle which is so-called super sport, and such as one to be a base vehicle for competition, how to improve an acceleration performance exerts a large influence. As one method of improving the acceleration performance, there is a method in which a period of time of omission of driving force which is inevitably generated at a time of gear shift is reduced to be an extremely short period of time.
Conventionally, a method of detecting a rotation of shift rod by a switch, and a method of disposing load sensors of load cell type on a shift rod and understanding an intention of a rider that he/she tries to perform a gear shift by detecting signals or load values of the sensors, have been known. A method in which, based on such signals, an engine output is reduced for a moment by an ignition misfire, an ignition delay or the like of an ignition plug through a control of an ECU (Engine Control Unit), thereby making a gear shift to be performed in the moment in which an engagement force of gear dog is reduced, has been adopted.
For example, in the disclosed Patent Document 1, it is designed such that in a gear shift mechanism of a motorcycle, a shift load sensor which detects an operating load at a time of shifting is attached to a link member to detect an operating state of a shift pedal. Further, Patent Document 2 discloses this type of mechanism or device.
[Patent Document 1] Utility Model Registration Publication No. 2544067
[Patent Document 2] Japanese Laid-open Patent Publication No. 03-290031
The conventional devices use the load sensors of load cell type, and the sensors of load cell type are generally expensive and have problems such that noises due to engine vibration are output from the sensors, or the durability with respect to the vibration is not always sufficient.
Further, the sensor of load cell type does not extend or contract due to its structure, so that in a process of applying a load, a rotational force is generated on a gear shift lever. Further, when a force at which mutual gear dogs are engaged is weak at a rotation speed at which a generation of driving force is small, an erroneous operation of unintended gear shift easily occurs. Further, since a sensor main body does not extend or contract, there is a problem such that, when an operating load of a rider is small or when a period of time in which the operating load is applied is short, for example, the operating load is reduced during a rotation of the gear shift lever, and if no measure is taken, the gear shift is not properly completed.
Meanwhile, regarding the load sensor of switch type, two of the sensors have to be provided for disposing the sensors for both of a shift-up and a shift-down, and thus a size thereof is inevitably increased. Further, switch signals are used for determination, so that there is a problem such that when, for example, a load applied to a gear shift lever and a shift rod is varied during a gear shift, the switch signal is generated at an unintended time.
Further, the device related to Patent Document 1 is one that detects a shift-up state, so that in order to detect a shift-down, there is a need to additionally provide a sensor for load in a direction opposite to that of the shift-up to the link member. In that case, there is a problem such that a size of the device and the number of parts are inevitably increased, which leads to an increase in cost.